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<topic id="topic1" xml:lang="en"><title id="gu143896">pg_listener</title><body><p>The <codeph>pg_listener</codeph> system catalog table supports the <codeph>LISTEN</codeph> and
        <codeph>NOTIFY</codeph> commands. A listener creates an entry in
        <codeph>pg_listener</codeph> for each notification name it is listening for. A notifier
      scans and updates each matching entry to show that a notification has occurred. The notifier
      also sends a signal (using the PID recorded in the table) to awaken the listener from
      sleep.</p><p>This table is not currently used in Greenplum Database.</p><table id="gu143898"><title>pg_catalog.pg_listener</title><tgroup cols="4"><colspec colnum="1" colname="col1" colwidth="131pt"/><colspec colnum="2" colname="col2" colwidth="86pt"/><colspec colnum="3" colname="col3" colwidth="85pt"/><colspec colnum="4" colname="col4" colwidth="147pt"/><thead><row><entry colname="col1">column</entry><entry colname="col2">type</entry><entry colname="col3">references</entry><entry colname="col4">description</entry></row></thead><tbody><row><entry colname="col1"><codeph>relname</codeph></entry><entry colname="col2">name</entry><entry colname="col3"/><entry colname="col4">Notify condition name. (The name need not match
any actual relation in the database.</entry></row><row><entry colname="col1"><codeph>listenerpid</codeph></entry><entry colname="col2">int4</entry><entry colname="col3"/><entry colname="col4">PID of the server process that created this
entry.</entry></row><row><entry colname="col1"><codeph>notification</codeph></entry><entry colname="col2">int4</entry><entry colname="col3"/><entry colname="col4">Zero if no event is pending for this listener.
If an event is pending, the PID of the server process that sent the notification.</entry></row></tbody></tgroup></table></body></topic>